There has heretofore been developed a gravity conveyor of the type including upper and lower return and advance inclined guideway sections positioned one above the other, with opposite adjacent ends converging and diverging respectively. Each section supports a number of load holding trolleys which roll from the high end of each section of the guideway to the opposite end. The trolleys are driven to an elevated position above an unload end of the inclined lower section for gravity return along the upper section to the load end of the conveyor section via a radiused track end section at the lower end of the upper section. Another radiused track end section allows movement of the trolleys down to the lower section at the other end.
It is sometimes desirable that such conveyors be used as "accumulators" in which a series of the trolleys is allowed to queue up at the unload end enabling a stock piled or "float" quantity of parts at the unload end of the conveyor lower section. Such queuing has created problems in the mechanism used to elevate the trolleys to the upper end of the return section of the conveyor since reliable engagement with an individual trolley is rendered more difficult by the presence of the other queued trolleys.
Accordingly, it is an object of the present invention to provide a trolley drive mechanism for moving the trolleys around the radiused end sections of the gravity conveyor in which the individual trolleys are reliably engaged notwithstanding the presence of other queued trolleys presented for return to the upper return section of the conveyor.